The invention relates to a vehicle with a laterally mounted optical scanning device for zero-contact scanning of a lateral road area, with an evaluation unit connected thereto.
Zero-contact scanning systems of this generic type are already known in many forms and serve primarily to detect obstacles, give distance warnings, monitor rear areas, and/or detect road markings. Such systems are used, for example, for automatically keeping the vehicle in its lane or as a warning against falling asleep. In the latter case, upon detecting an imminent departure of the vehicle from the lane, the system generates an optical, acoustic, and/or haptic warning signal.
Thus U.S. Pat. No. 4,970,653, for example, discloses a vehicle with an optical scanning system that comprises a conventional CCD camera that scans the area ahead of the vehicle, i.e. the current lane including the lane markings on either side. An evaluation unit connected thereto, which contains an image processing computer, evaluates the image to determine the positions of the lateral lane markings as well as any obstacles in the lane, in the near vicinity in front of the vehicle, and generates corresponding warning signals if an obstacle is detected or the vehicle is about to cross a lane marking. The lane marking recognition function can also be used to limit obstacle recognition to the area between the markings of the lane occupied by the vehicle or to keep the vehicle automatically in the current lane.
German patent document DE-OS 33 00 086 A1 teaches equipping the anterior lateral area of a motor vehicle with an optical scanning device in which photosensitive sensors scan the road area directly beneath them, which is illuminated by a light source mounted on the vehicle and shining downward, for example. To warn the driver of uncontrolled driving, this known device delivers a warning signal when the vehicle crosses a lateral boundary marking in the lane occupied by the vehicle and therefore when the optical scanning device detects such a boundary marking.
German patent document DE-OS 38 27 729 A1 discloses a collision warning system for motor vehicles which comprises a distance measuring device for zero-contact detection of distance and position of an obstacle in the area traversed by the vehicle and, on detecting a danger of collision, produces an acoustic and/or optical warning signal. The collision warning device for example includes scanners mounted on the front right and rear left corners of the vehicle, with each scanner comprising an ultrasonic sensing unit and an infrared sensing unit. The ultrasonic sensing units each cover an angle range of 270.degree. and measures distance using the pulse-echo method. The infrared sensing units each generate a narrow infrared beam which is pivoted stepwise through the corresponding 270.degree. angle range to detect obstacles.
The object of the present invention is to provide a vehicle mounted system of the type described above in which the design of the optical scanning device permits reliable scanning of a lateral lane area for various functions such as warning against falling asleep and automatically staying in a lane, as well as a system reaction that is suitable for the type of lane marking and/or boundary that exists, in the form of a warning signal, for example.
This goal is achieved by the vehicle mounted scanner system according to the invention, which incorporates as an optical scanning device, a linear array of infrared transmitting elements, with an associated CCD array. An evaluation unit connected to the optical scanning device is designed for elapsed time measurement as well as contrast determination and contour recognition. This system scans the surface of the lane to detect any existing lane boundary. The running time and contrast determination permit recognition of lateral lane markings, and determination of the distance of the vehicle therefrom in a manner described hereinafter. This system can therefore warn against falling asleep or against an imminent crossing of a lateral lane marking. It also constitutes the basis for a system for automatically staying in a lane, by which the vehicle can be kept automatically in a given lane.
An especially characteristic feature of the optical scanning system is that it also permits contour recognition by means of the individual infrared transmitting elements that are arranged in a linear array, infrared LEDs for example. This means that the system can recognize the type of lateral lane boundary and can distinguish whether it is a line marking separating an adjacent travel or breakdown lane, a curb, or an adjacent grassy area in the absence of a fixed lane boundary, etc.
The capability of contour recognition makes it possible, when there is a risk of crossing a lane boundary, to select the warning time as a function of the type of lane boundary recognized. In this manner, if the vehicle is drifting out of the lane, it is possible to give the driver sufficient time and space to return the vehicle safely to the lane. The scanning device can be arranged to monitor a lateral stripe which extends above the level of a lane stripe marking in order to detect the type of lane boundary on the outside.
Based the results of the travel time and contrast measurement, as well as contour recognition, obstacle recognition of fixed or movable obstacles in the vicinity of the vehicle can also be performed and used profitably, especially in commercial vehicles which generally have large blind spots for the driver in the immediate vicinity of the vehicle.
In a first embodiment of the invention, the additional measurement of the vehicle's transverse speed offers an especially advantageous warning system against the driver's falling asleep, with a warning signal being delivered immediately prior to the vehicle's drifting out of the lane as a function of the transverse speed of said vehicle, the longitudinal speed of the vehicle, and optionally also of the type of lane boundary detected. Triggering of the warning can then be better adapted to the individual situation than in systems in which the warning is triggered only when the distance from the lane marking is detected.
In another embodiment of the invention, imminent crossing of a lateral lane marking is monitored on both sides, and an acoustic warning is emitted on the side of the vehicle to which the vehicle is drifting. The acoustic warning can consist for example of the sound of a rumble strip, which indicates acoustically to the driver that he is crossing a lane marking studded with bumps, or a corrugated strip.
According to another embodiment, upon demand from the driver, the vehicle can be kept automatically in a given lane. For this purpose, the optical scanning system that detects the lateral lane markings has its evaluation unit coupled to a device that regulates the distance of the vehicle from one or both lateral lane markings according to preset values, by corresponding automatic steering intervention. This automatic lane-maintenance function can be activated and deactivated by the driver in a manner similar to that known for example from a conventional cruise control device for controlling vehicle speed.
Yet another advantageous embodiment ensures that the automatic lane maintenance function can be activated only when a suitable driving situation exists, for example only when there are lane markings that can be recognized sufficiently reliably. Since it is advisable to deactivate the distance-regulating device when a driver's steering intervention is recognized, a passing maneuver is recognized, or when brake activation is recognized, priority may automatically be given to these driver actions.
A further improvement, permits additional performance of a rear-area and/or environment monitoring function by the optical scanning devices mounted on both sides and having infrared transmitting elements connected side by side, possibly in connection with additional scanning units mounted on the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.